Video is now a common component of multimedia communications and in an attempt to transmit video sequences efficiently over communication channels video sequences are typically encoded and compressed. Typically, video sequences are compressed according to video compression standards such as H.263 and MPEG-4. Such compression standards exploit the temporal and spatial redundancies in a video sequence to reduce the bandwidth required for transmission. For example, two consecutive frames in a video sequence often differ only slightly and compression techniques may take advantage of the redundancy in the two frames by only encoding the differences between these frames.
In general, a frame is analyzed at a block level where a block typically comprises an 8 by 8 array of pixels of the image. Usually, compression is conducted at the block level and only blocks of a current frame that are identifiably different to corresponding image blocks in the immediately preceding decoded frame are coded and transmitted (or coded and stored for later use). Blocks that are substantially unchanged are simply identified and a simple flag is set or a field coded in the coded bit streams. When the coded bit streams are later decoded for providing an image, the decoded image is in the form of a YUV image that is then processed into a RGB image by a color conversion technique. However, known color conversion techniques do not exploit the redundancy associated with the substantially unchanged respective blocks of consecutive frames.
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